Cardiac catheterization procedures are well known for diagnosis and therapy relating to lesions in the cardiovascular system. One such procedure is angioplasty, for eliminating or ameliorating vascular plaque blockage or constriction in vessels which carry the heart's blood supply. In an angioplasty procedure, an expandable balloon is introduced into the patient's arterial system and advanced until it is positioned in the region of the blockage or constriction. Once so positioned, i.e., "emplaced", the balloon is expanded by filling it with a liquid. In successful procedures, the expandable balloon presses outwardly against the walls of the artery and expands the artery to a degree to which the artery is either partially or totally re-opened to blood flow.
A typical angioplasty procedure, and components used in practicing the procedure, are now described.
Prior to initiating the angioplasty procedure, a guiding catheter is placed, typically via the femoral artery, into the aorta and its tip is advanced to the entrance of the coronary arteries which branch from the aorta. This entrance into the coronary arteries is called the "ostium". Once placed, the guiding catheter acts as a conduit to access the coronary arteries with a balloon guidewire and balloon catheter. The guiding catheter is a portion of plastic tubing having a length of about 95 centimeters, an inside diameter of about 0.08 inches, and an outside diameter of about 2.5 millimeters.
The physician, in one known procedure, threads a balloon catheter onto a balloon guidewire. This operation takes place external to the patient.
The balloon guidewire is a piece of stainless steel and platinum wire, approximately 175 centimeters in length, and about 0.010-0.018 inches in diameter. The soft distal tip of the guidewire can be shaped to form a "J" configuration. This "J" shape allows the physician to steer the wire by twisting the proximal extremity of the wire while advancing or retracting the wire.
One type of balloon catheter is an elongated flexible plastic member defining two longitudinal passages and having a balloon located near its distal end. One longitudinal passage defines a closed tubular sleeve through which the balloon guidewire can be passed, and which completely surrounds the balloon guidewire over most of the catheter's length. The other longitudinal passage defines a conduit communicating with the interior of the balloon and through which inflation fluid can be injected to inflate the balloon. The passage defining the sleeve for accommodating a guidewire is often called the "guidewire lumen". The passage defining the conduit for inflation fluid is often called the "inflation lumen".
Balloon catheters having a closed tubular guidewire lumen enclosing the balloon guidewire over most of its length are called "over the wire" catheters.
Among the types of over the wire balloon catheters is one of a type in which the two longitudinal passages are generally side by side and parallel. In another type of over the wire balloon catheter, the two longitudinal passages are co-axial. In this latter type, the balloon guidewire is passed down the inner central passage and the inflation fluid is injected into the balloon via the outer passage.
Balloon catheters of another type, sometimes called "on the wire" catheters, as well as associated apparatus and method for use in angioplasty, are described in U.S. Pat. No. 5,040,548, issued on Aug. 20, 1991, to Yock, and U.S. Pat. No. 4,762,129, issued on Aug. 8, 1988. Each of these issued U.S. patents is hereby expressly incorporated by reference.
The physician, in using an over the wire balloon catheter, passes the balloon guidewire through the appropriate one of the longitudinal passages in the balloon catheter, leaving a portion of the balloon guidewire extending from the distal end of the balloon catheter and also a portion extending from its proximal end.
This assembly is then inserted into the proximal end of the guiding catheter, distal end first. The assembly is inserted until the balloon which is attached near the distal end of the balloon catheter is near the distal end of the guiding catheter. At this point, the physician, while maintaining the balloon catheter stationary, pushes on the balloon guidewire to advance it outwardly from the distal end of the guiding catheter.
The balloon guidewire can be steered by appropriate twisting movement by the physician.
The physician steers the balloon guidewire into the chosen one of the coronary arteries, and advances it until it reaches a location of constriction which the physician desires to re-open. Carefully, the physician eases the balloon guidewire through the region of restriction until a portion of the balloon guidewire is beyond the constriction, relative to the guiding catheter.
With the balloon guidewire held stationary, the physician then advances the balloon catheter. The distal end of the balloon catheter, as it is advanced, will, of course, follow the balloon guidewire which is already in place.
The physician continues to advance the balloon until it is located in the region of constriction of the artery. With the balloon and its associated catheter held stationary, inflation fluid is injected into the conduit which communicates with the balloon, causing it to inflate. Inflation of the balloon expands the walls of the artery in the region of constriction and, in successful procedures, re-opens the artery to sufficient blood flow.
Arteries vary in size, and therefore balloon catheters having balloons of different sizes are provided for the physician's selection. These balloons, when inflated, range from about 1.5 millimeters to about 4 millimeters in diameter.
Sometimes, it is necessary for the physician to use more than one balloon to open an artery. Sometimes, the chosen balloon is too large to be advanced into the constricted area. In other instances, the first chosen balloon size, even when inflated, is not large enough to open the constricted area to the degree desired. In such cases, it is necessary to exchange one balloon for another during the same angioplasty procedure.
In order to accomplish this exchange, the balloon guidewire is left in place, and the balloon catheter is withdrawn entirely from the guiding catheter until it is completely disengaged from the balloon guidewire. A new balloon catheter, having a different sized balloon, is then re-inserted over the balloon guidewire and advanced back to the location of the constricted area, where it is used to effect the desired result.
Once the balloon guidewire is initially in place, extending past the constricted area, it is highly desirable to leave the balloon guidewire in place for the entire remainder of the angioplasty procedure. This means that the balloon guidewire must remain in place even during exchanges of balloons. The reason for this is that, when a foreign object, such as the balloon guidewire, is introduced into an artery, the artery walls sometimes go into spasm, and constrict generally along a substantial portion of its length. If the artery tends to contract in this way, removal of the balloon guidewire while the artery is so contracted will sometimes render it virtually impossible to reinsert the guidewire through the contracted artery.
Withdrawal of the balloon catheter, while preventing movement of the balloon guidewire, is a difficult and cumbersome procedure. This procedure has required both a second individual, in addition to the physician, and the attachment of a removable extension to the proximal end of the guidewire.
In the catheter exchange procedure, removal of the catheter, and the insertion of the new catheter, is done manually. This is a two-hand operation for the physician. In addition, an attendant must hold the balloon guidewire longitudinally fixed with respect to the patient during the catheter exchange procedure.
Holding the balloon guidewire longitudinally fixed has been a difficult task. One reason for this is that, when the catheter to be removed is being slid proximally along the guidewire, friction between the balloon catheter and the balloon guidewire tends to dislodge the balloon guidewire and move it in the proximal direction. As pointed out above, it is undesirable that the balloon guidewire move longitudinally during the exchange operation.
When a new catheter is being threaded upon an indwelling balloon guidewire, frictional forces tend to be generated which urge the balloon guidewire toward longitudinal movement in the distal direction. This, too, is undesirable.
It is a general object of the present invention to provide apparatus for facilitating rapid catheter exchange in a vascular dilatation procedure.